A directional flow cvi flow field structure and carbon-carbon composite production process

Abstract

The application discloses a directional flow CVI flow field structure and a carbon-carbon composite material production process, which comprises an air inlet assembly and a movable plate assembly, and the air inlet assembly and the movable plate assembly are arranged in the interior of a deposition cover; the movable plate assembly comprises a first movable plate, the first movable plate is arranged perpendicularly to the air inlet assembly and is in sliding connection with the air inlet assembly, the first movable plate comprises a first lower movable plate arranged below the air inlet assembly and a first upper movable plate arranged above the air inlet assembly, and the first movable plate is slid on the air inlet assembly to change the air inlet area of the air inlet assembly, so as to adapt to the densification processing of different preforms; the movable plate assembly is arranged to slide in the deposition cover, and the areas of the deposition area and the air inlet area are synchronously changed, so that the position of the movable plate assembly can be adjusted according to the size and the number of different preforms, narrow gap flow is realized, and the preform surface is not easy to form a crust in the pyrolytic carbon deposition process, so that the plate material can be rapidly deposited to a relatively high density at one time.

Description

Technical Field

[0001] This invention relates to the field of CVI production of carbon-carbon composite materials, specifically to a directional flow CVI flow field structure and a carbon-carbon composite material production process. Background Technology

[0002] Chemical vapor infiltration (CVI) process for carbon / carbon composites involves placing a carbon fiber preform of a specific shape in a deposition furnace, using nitrogen or argon as a carrier and hydrocarbon gas as a carbon source. Under certain temperature and pressure, the gaseous carbon source enters the preform through diffusion and flow. Under high temperature, it undergoes a pyrolysis reaction due to thermal activation, generating pyrolytic carbon which is deposited on the fiber surface as a coating. Ultimately, the coatings overlap to form a continuous phase within the material.

[0003] Currently, chemical vapor deposition densification equipment is becoming increasingly larger, leading to a corresponding increase in the amount of material loaded into the furnace. This increased furnace size and load result in uneven density in carbon / carbon composite products, preventing the full utilization of carbon source gas. Furthermore, when the load is small or the preform itself is small, the utilization rate of carbon source gas is further reduced, resulting in waste of carbon source gas, increased costs, and the inability of carbon source gas to deposit properly. Ultimately, due to corrosion from silicon vapor, it becomes necessary to replace the product prematurely, causing significant losses. Summary of the Invention

[0004] To address the shortcomings of existing technologies, a directional flow CVI flow field structure and carbon-carbon composite material production process are proposed. This solves the problem in the background technology where the utilization rate of carbon source gas is further reduced and carbon source gas is wasted when the loading amount is small or the size of the preform itself is small.

[0005] To achieve the above objectives, the present invention proposes the following technologies:

[0006] A directional flow CVI flow field structure includes an air inlet assembly and a movable plate assembly, which are disposed inside a deposition hood. The movable plate assembly includes a first movable plate, which is perpendicular to the air inlet assembly and slidably connected to it. The first movable plate includes a first lower movable plate located below the air inlet assembly and a first upper movable plate located above the air inlet assembly. The first movable plate slides on the air inlet assembly to change the air inlet area of ​​the air inlet assembly, adapting to the densification of different preforms.

[0007] Furthermore, the first upper movable plate and the first lower movable plate are connected by a connecting block, which is slidably connected to the inner wall of the deposition cover.

[0008] Furthermore, the air intake assembly includes an air intake perforated plate and an air intake array perforated plate. The air intake array perforated plate is located above the air intake perforated plate to form an air intake plate. The connecting block is snapped onto one side of the air intake plate and is slidably connected to the air intake plate.

[0009] Furthermore, two first movable plates are symmetrically arranged around the center of the deposition hood, and sliding blocks are respectively arranged above the two first lower movable plates. The sliding blocks are slidably connected in the groove opened below the air intake assembly. The two sliding blocks are respectively threaded to the two ends of the first adjusting rod, and the two ends of the first adjusting rod are provided with threads with opposite directions of rotation.

[0010] Furthermore, the movable plate assembly also includes a second movable plate disposed perpendicular to the first movable plate. The second movable plate is snapped onto the inner wall of the deposition hood and slidably connected to the deposition hood. The second movable plate is provided with a snapping block for snapping onto the air intake assembly.

[0011] Furthermore, several second movable plates are provided, and these second movable plates are symmetrically arranged on both sides of the first movable plate. When the second movable plate is engaged with the air intake assembly, the inner surface of the second movable plate is flush with the two end faces of the first movable plate.

[0012] Furthermore, the second movable plate is slidably connected to the first movable plate, and the two snap-fit ​​blocks are respectively threaded to both ends of the second adjusting rod. The second adjusting rod passes through the air intake assembly and is rotatably connected to the air intake assembly. The two ends of the second adjusting rod are provided with threads of opposite directions.

[0013] Furthermore, the deposition cover is provided with an adjustment hole, and the two snap-fit ​​blocks that are threadedly connected to the second adjustment rod are provided with mounting holes. The other snap-fit ​​blocks are provided with mounting grooves. The height of the mounting grooves is less than the height of the adjustment hole. Limiting rods are detachably installed in the mounting holes and mounting grooves. Several sets of limiting rods are provided.

[0014] Furthermore, an air outlet assembly is provided above the deposition hood, the air outlet assembly includes an air outlet porous plate and an air outlet array plate, the air outlet array plate is located below the air outlet porous plate, the movable plate assembly is slidably connected to the air outlet array plate, a partition is provided below the deposition hood, the movable plate assembly is slidably connected to the partition, and an air inlet is provided on the partition.

[0015] A carbon-carbon composite material production process, adapted to the directional flow CVI flow field structure described in any one of claims 1-9, includes the following steps:

[0016] Carbon fiber preforms were prepared using the S1 three-dimensional braiding method, with the density of the carbon fiber preforms controlled between 0.43 and 0.45 g / cm³. 3 between;

[0017] S2 treats the carbon fiber preform at 300℃ to harden the soft fibers into a hard state.

[0018] S3 adjusts the flow field structure of the directional flow CVI according to the size of the carbon fiber preform, places the carbon fiber preform into the deposition furnace, and then evacuates to <1KPa to remove air from the furnace and ensure the vacuum level inside the furnace.

[0019] S4 is heated to 1000-1100℃, and the vacuum degree is maintained at 2.5-3KPa. Then, carbon source gas is introduced and 20% nitrogen is mixed in as a carrier gas to improve density uniformity.

[0020] When the S5 process is 2 / 3 complete, change the furnace pressure to 2-2.5 kPa to avoid large-area crusting and carbon black formation due to restricted airflow.

[0021] After the S6 densification process is completed, the vacuum system is shut off, and nitrogen protective gas is introduced to atmospheric pressure. The gas is continuously introduced until the furnace temperature drops to room temperature, at which point the nitrogen introduction is stopped, and carbon / carbon composite material is obtained.

[0022] Compared with existing technologies, the comprehensive effects of this invention include: setting the air intake component inside the deposition hood, forming a deposition area above the air intake component, and forming an air intake area between the air intake component and the deposition hood; the movable plate component slides inside the deposition hood, synchronously changing the area of ​​the deposition area and the air intake area, thereby adjusting the position of the movable plate component according to the size and number of different preforms, ensuring that the gaps between the preforms are small enough to ensure that the carbon source gas fully passes through the surface of the preforms, improving the density and uniformity, while ensuring that the preforms are closely arranged and distributed in the deposition area, so that the carbon source gas entering the deposition hood fully passes through the placement position of the preforms, improving the utilization rate of the carbon source gas, improving the density and uniformity of the preforms, improving the preparation quality of carbon-carbon composite materials, achieving narrow-slit flow, and preventing the surface of the preforms from crusting during the pyrolysis carbon deposition process, thus enabling the plate to be deposited to a relatively high density in one go. Attached Figure Description

[0023] Figure 1 This is a front view schematic diagram of the internal structure of Embodiment 1 of the present invention;

[0024] Figure 2 This is a schematic diagram of the first movable plate structure in Embodiment 1 of the present invention;

[0025] Figure 3 This is a side view of the internal structure of Embodiment 1 of the present invention;

[0026] Figure 4 This is a top view schematic diagram of the internal structure of the prefabricated body in Embodiment 1 of the present invention;

[0027] Figure 5 This is a front view schematic diagram of the internal structure of Embodiment 2 of the present invention;

[0028] Figure 6 This is a schematic diagram of the internal structure of the second movable plate connecting the air intake assembly in Embodiment 2 of the present invention;

[0029] Figure 7 This is a top view of the internal structure of the prefabricated body in Embodiment 2 of the present invention;

[0030] Figure 8 This is a front view schematic diagram of the internal structure of Embodiment 3 of the present invention;

[0031] Figure 9 This is a schematic diagram of the internal structure of the second movable plate connecting the air intake assembly in Embodiment 3 of the present invention;

[0032] Figure 10 This is a top view of the internal structure of the prefabricated body in Embodiment 3 of the present invention;

[0033] Figure 11 This is a schematic diagram of the protruding part structure in Embodiment 3 of the present invention;

[0034] Figure 12 This is a side view of the internal structure of Embodiment 3 of the present invention.

[0035] Legend: 1. Deposition hood; 2. First movable plate; 3. Connecting block; 4. Inlet perforated plate; 5. Inlet array perforated plate; 6. Sliding block; 7. First adjusting rod; 8. Second movable plate; 9. Snap-fit ​​block; 10. Second adjusting rod; 11. Adjusting hole; 12. Mounting groove; 13. Limiting rod; 14. Exhaust assembly; 15. Partition plate. Detailed Implementation

[0036] The technical solutions in the embodiments of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0037] In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Terms such as "upper," "lower," "left," "right," and "top" indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are used only for the convenience of describing the invention and for simplification, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention.

[0038] Example 1:

[0039] like Figures 1 to 4 As shown, a directional flow CVI flow field structure includes an air intake assembly and a movable plate assembly. The air intake assembly and the movable plate assembly are disposed inside the deposition hood 1. The movable plate assembly includes a first movable plate 2, which is disposed perpendicular to the air intake assembly and slidably connected to the air intake assembly. The first movable plate 2 includes a first lower movable plate located below the air intake assembly and a first upper movable plate located above the air intake assembly. The first movable plate 2 slides on the air intake assembly to change the air intake area of ​​the air intake assembly, adapting to the dense processing of different preforms.

[0040] An air intake assembly is located inside the deposition hood 1. A deposition area is formed above the air intake assembly, and an air intake area is formed between the air intake assembly and the deposition hood 1. A first movable plate 2 slides inside the deposition hood 1, and the left and right sidewalls of the first movable plate 2 slide against the left and right inner walls of the deposition hood 1 to simultaneously change the area of ​​the deposition area and the air intake area. This allows the first movable plate 2 to be adjusted according to the size and number of different preforms, ensuring that the gaps between the preforms are small enough to allow the carbon source gas to fully pass through the surface of the preforms, improving the density and uniformity. At the same time, it reduces the distance between the preforms and the peripheral walls of the deposition area, allowing the preforms to be closely arranged and distributed within the deposition area. This ensures that the carbon source gas entering the deposition hood 1 fully passes through the placement position of the preforms, improving the utilization rate of the carbon source gas, increasing the density and uniformity of the preforms, and improving the quality of carbon-carbon composite material preparation.

[0041] In the directional flow CVI flow field structure of this embodiment, the first upper movable plate and the first lower movable plate are connected by a connecting block 3. The connecting block 3 is slidably connected to the inner wall of the deposition hood 1. The air intake assembly includes an air intake perforated plate 4 and an air intake array perforated plate 5. The air intake array perforated plate 5 is located above the air intake perforated plate 4 to form an air intake plate. The connecting block 3 is snapped onto one side of the air intake plate and is slidably connected to the air intake plate.

[0042] The first upper movable plate and the first lower movable plate are connected by connecting blocks 3 on both sides to form the first movable plate 2. At the same time, they are snapped onto the air intake perforated plate 4 and the air intake array perforated plate 5 by connecting blocks 3. Correspondingly, the inner wall of the deposition hood 1 is provided with a groove that matches the connecting block 3 so that the connecting block 3 can slide to change the position of the first movable plate 2 and adjust the size of the deposition area.

[0043] The inlet perforated plate 4 has tapered horn-shaped holes, with the cone base or horn opening facing the preform. This suppresses jet generation and uniformly disperses the airflow. The uniformly dispersed airflow finally enters the deposition area containing the preform through the inlet array perforated plate 5. The diameter of the dispersion holes on the inlet array perforated plate 5 is much smaller than the tapered horn holes on the inlet perforated plate 4, and the cone base of each tapered horn hole corresponds to multiple dispersion holes. This ensures that the airflow is dispersed as uniformly as possible to flow through the narrow gaps between the plates.

[0044] In the directional flow CVI flow field structure of this embodiment, two first movable plates 2 are arranged symmetrically with respect to the center of the deposition hood 1. Sliding blocks 6 are respectively arranged above the two first lower movable plates. The sliding blocks 6 are slidably connected in the groove opened below the air intake assembly. The two sliding blocks 6 are respectively threaded to the two ends of the first adjusting rod 7. The two ends of the first adjusting rod 7 are provided with threads with opposite directions of rotation.

[0045] Two first movable plates 2 are set and threadedly connected to a first adjusting rod 7 with threads. By rotating the first adjusting rod 7, the sliding block 6 is driven to slide in the groove, thereby changing the distance between the two first movable plates 2. The two symmetrical first movable plates 2 are set to ensure that the air intake area and the deposition area are located in the middle position inside the deposition hood 1, ensuring that the preform is evenly distributed in the deposition hood 1, and that the distance between the preform and the outer edge of the deposition hood 1 and the first movable plates 2 is balanced. This makes the preform heat up evenly in the deposition hood 1, and the carbon source gas reacts and deposits better on the preform in the deposition area, improving the utilization rate of the carbon source gas and improving the densification effect.

[0046] Example 2:

[0047] like Figures 5 to 7 As shown, based on Embodiment 1, in the directional flow CVI flow field structure of this embodiment, the movable plate assembly further includes a second movable plate 8 arranged perpendicular to the first movable plate 2. The second movable plate 8 is snapped onto the inner wall of the deposition hood 1 and slidably connected to the deposition hood 1. The second movable plate 8 is provided with a snapping block 9 for snapping onto the air intake assembly.

[0048] In Embodiment 1, since the connecting blocks 3 on both sides of the first movable plate 2 need to be slotted on the inner wall of the deposition cover 1, and the width of the connecting block 3 is much smaller than the width of the slot, the deposition area and the air intake area are directly connected through the gap between the two connecting blocks 3 on the same slot. When carbon source gas is introduced, the airflow of carbon source gas entering the deposition area from the gap and entering the deposition area through the air intake component may be disturbed, affecting the reaction and deposition of carbon source gas.

[0049] By setting a second movable plate 8 perpendicular to the first movable plate 2, and setting a snap-fit ​​block 9 on the second movable plate 8 whose shape matches the height of the air intake component, after the first movable plate 2 is adjusted to an appropriate position according to the size and quantity of the preform to be processed, the second movable plate 8 is moved so that the snap-fit ​​block 9 snaps onto the air intake component, thus blocking the gap between the air intake component and the inner wall of the deposition hood 1, so that the first movable plate 2 and the second movable plate 8 form a closed deposition area, ensuring that the carbon source gas enters the deposition area from the air intake area through the air intake component, thereby improving the utilization rate of the carbon source gas and improving the density quality.

[0050] Preferably, an adjustment hole is provided on the deposition cover 1 corresponding to the second movable plate 8. An adjustment rod matching the size of the adjustment hole is inserted into the adjustment hole, and the adjustment rod is pushed to push the locking block 9 to drive the second movable plate 8 to slide inside the deposition cover 1, so that the second movable plate 8 is locked with the air intake assembly.

[0051] In the directional flow CVI flow field structure of this embodiment, several second movable plates 8 are provided, and several second movable plates 8 are symmetrically arranged on both sides of the first movable plate 2. When the second movable plate 8 is engaged with the air intake assembly, the inner surface of the second movable plate 8 is flush with the two end faces of the first movable plate 2.

[0052] By setting up several symmetrically distributed second movable plates 8, and determining the number of second movable plates 8 to be adjusted based on the distance between two first movable plates 2 and the width of each second movable plate 8, the second movable plates 8 are set up separately, increasing the range of adjustment for the deposition area. The smaller the width of the second movable plate 8, the larger the range of adjustment for the distance between two first movable plates 2, thus enabling a larger adjustment range for the deposition area and the immediate surrounding area. Consequently, with a fixed precast size and spacing, the smaller the distance between the precast and the surrounding walls of the deposition area, the more concentrated the carbon source gas flow and the closer the contact with the precast, thereby improving the carbon source gas utilization rate and the more significant the densification effect.

[0053] In the directional flow CVI flow field structure of this embodiment, the second movable plate 8 is slidably connected to the first movable plate 2, and the two snap-fit ​​blocks 9 are respectively threaded to the two ends of the second adjusting rod 10. The second adjusting rod 10 passes through the air intake assembly and is rotatably connected to the air intake assembly. The two ends of the second adjusting rod 10 are provided with threads with opposite directions of rotation. By rotating the second adjusting rod 10, the first movable plates 2 on both sides are driven to slide inside the deposition hood 1.

[0054] Example 3:

[0055] like Figures 8 to 12 As shown, based on Embodiment 2, in the directional flow CVI flow field structure of this embodiment, the deposition cover 1 is provided with an adjustment hole 11, the two snap-fit ​​blocks 9 that are threadedly connected to the second adjustment rod 10 are provided with mounting holes, and the other snap-fit ​​blocks 9 are provided with mounting grooves 12. The height of the mounting grooves 12 is less than the height of the adjustment hole 11. Limiting rods 13 are detachably installed in the mounting holes and mounting grooves 12, and several sets of limiting rods 13 are provided.

[0056] Preferably, the deposition hood 1 has protrusions on both sides, with movable grooves inside the protrusions. The snap-fit ​​blocks 9 are slidably connected to the protrusions, and adjustment holes 11 are opened on the protrusions. The snap-fit ​​blocks 9, which are threadedly connected to the second adjustment rod 10, have mounting holes on both sides. By inserting limiting rods 13 of different lengths into the mounting grooves 12 and mounting holes, the second movable plates 8 are partially limited. By rotating the second adjustment rod 10, the snap-fit ​​blocks 9 threadedly connected to it slide in the deposition hood 1. At the same time, through the cooperation of the mounting holes and the limiting rods 13, multiple snap-fit ​​blocks 9 and the second movable plates 8 move synchronously, which facilitates the simultaneous adjustment of the distance between the second movable plates 8.

[0057] The protrusion provides a certain length for the locking block 9, and the groove on the locking block 9 that engages with the air intake component has a certain depth. As the engagement depth between the locking block 9 and the air intake component changes, the sliding distance of the second movable plate 8 on the air intake component becomes adjustable. That is, the distance between the two second movable plates 8 can be adjusted. When the distance between the first movable plates 2 is adjusted to change the width of the deposition area, the distance between the second movable plates 8 is adjusted to change the length of the deposition area. This further increases the adjustable range of the deposition area and the air intake area, which can accommodate preforms of different lengths with a certain thickness. It is also convenient to control the gap between the preform and the second movable plate 8, improve the utilization rate of carbon source gas, and expand the application range of the flow field.

[0058] In the directional flow CVI flow field structure of this embodiment, an exhaust assembly 14 is provided above the deposition hood 1. The exhaust assembly 14 includes an exhaust perforated plate and an exhaust array perforated plate. The exhaust array perforated plate is located below the exhaust perforated plate. The movable plate assembly is slidably connected to the exhaust array perforated plate. A partition 15 is provided below the deposition hood 1. The movable plate assembly is slidably connected to the partition 15. An air inlet is provided on the partition 15.

[0059] The reaction gas from the pyrolysis process is dispersed through the outlet perforated plate, which helps to eliminate gas accumulation and the formation of carbon black. The reacted gas then passes through the outlet perforated plate and exits the furnace chamber via the outlet porous plate. To prevent blockage, the diameter of the holes in both the outlet porous plate and the outlet array perforated plate must be larger than the corresponding inlet porous plate 4 and inlet array perforated plate 5. A partition 15 is provided, forming an inlet area between the partition 15 and the first movable plate 2 and the second movable plate 8. Preferably, the inlet is located in the middle of the partition 15. Multiple inlets can be provided, or the number of inlets can be adjusted according to the size of the area enclosed between the adjusted first movable plate 2 and the second movable plate 8. The carbon source gas enters the inlet area from the inlet, and the inlet area has sufficient space to ensure that the reaction gas is preheated to a certain temperature before entering the deposition area.

[0060] A carbon-carbon composite material production process, adapted to the above-mentioned directional flow CVI flow field structure, includes the following steps:

[0061] Carbon fiber preforms were prepared using the S1 three-dimensional braiding method, with the density of the carbon fiber preforms controlled between 0.43 and 0.45 g / cm³. 3 between;

[0062] S2 processes the carbon fiber preform at 300°C to harden the soft fibers into a hard state; the above steps ensure the stability of the preform.

[0063] S3 adjusts the flow field structure of the directional flow CVI according to the size of the carbon fiber preform, places the carbon fiber preform into the deposition furnace, and then evacuates to <1KPa to remove air from the furnace and ensure the vacuum level inside the furnace.

[0064] S4 is heated to 1000-1100℃ while maintaining a vacuum of 2.5-3KPa. Then, a carbon source gas is introduced, mixed with 20% nitrogen as a carrier gas to improve density uniformity. The gas is then heated to 1000-1100℃ while maintaining a vacuum of 2.5-3KPa. Natural gas is then introduced, and under the high-temperature atmosphere, it is cracked and adheres to the surface of the fiber pores to form deposited carbon. 20% nitrogen is mixed in as a carrier gas to improve density uniformity.

[0065] When the S5 process is 2 / 3 complete, change the furnace pressure to 2-2.5 kPa to avoid large-area crusting and carbon black formation due to restricted airflow. Control the rate of carbon source gas cracking by changing the deposition pressure to prevent carbon black crusting.

[0066] After the S6 densification process is completed, the vacuum system is shut off, and nitrogen protective gas is introduced to atmospheric pressure. The gas is continuously introduced until the furnace temperature drops to room temperature, at which point the nitrogen introduction is stopped, and carbon / carbon composite material is obtained.

[0067] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "setting," "connection," "fixing," "rotation," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Unless otherwise explicitly limited, those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0068] Although embodiments of the invention have been shown and described in detail, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A directional flow CVI flow field structure, characterized in that, It includes an air intake assembly and a movable plate assembly, which are disposed inside the deposition hood. The movable plate assembly includes a first movable plate, which is disposed perpendicular to the air intake assembly and slidably connected to the air intake assembly. The first movable plate includes a first lower movable plate located below the air intake assembly and a first upper movable plate located above the air intake assembly. The first movable plate slides on the air intake assembly to change the air intake area of ​​the air intake assembly, adapting to the densification of different preforms. The first upper movable plate and the first lower movable plate are connected by a connecting block, which is slidably connected to the inner wall of the deposition shroud; The movable plate assembly further includes a second movable plate that is perpendicular to the first movable plate. The second movable plate is snapped onto the inner wall of the deposition hood and slidably connected to the deposition hood. The second movable plate is provided with a snapping block for snapping onto the air intake assembly. The second movable plate is provided in several parts, and the several second movable plates are symmetrically arranged on both sides of the first movable plate. When the second movable plate is engaged with the air intake assembly, the inner surface of the second movable plate is flush with the two end faces of the first movable plate.

2. The directional flow CVI flow field structure according to claim 1, characterized in that, The air intake assembly includes an air intake perforated plate and an air intake array perforated plate. The air intake array perforated plate is located above the air intake perforated plate to form an air intake plate. The connecting block is snapped onto one side of the air intake plate and is slidably connected to the air intake plate.

3. The directional flow CVI flow field structure according to claim 1, characterized in that, Two first movable plates are symmetrically arranged around the center of the deposition hood. Sliding blocks are respectively arranged above the two first lower movable plates. The sliding blocks are slidably connected in the groove opened below the air intake assembly. The two sliding blocks are respectively threaded to the two ends of the first adjusting rod. The two ends of the first adjusting rod are provided with threads with opposite directions of rotation.

4. The directional flow CVI flow field structure according to claim 1, characterized in that, The second movable plate is slidably connected to the first movable plate, and the two snap-fit ​​blocks are respectively threaded to both ends of the second adjusting rod. The second adjusting rod passes through the air intake assembly and is rotatably connected to the air intake assembly. The two ends of the second adjusting rod are provided with threads of opposite directions.

5. The directional flow CVI flow field structure according to claim 4, characterized in that, The deposition cover has an adjustment hole, and the two snap-fit ​​blocks that are threadedly connected to the second adjustment rod have mounting holes. The other snap-fit ​​blocks have mounting grooves. The height of the mounting grooves is less than the height of the adjustment hole. Limiting rods are detachably installed in the mounting holes and mounting grooves. Several sets of limiting rods are provided.

6. A directional flow CVI flow field structure according to any one of claims 1-5, characterized in that, An air outlet assembly is provided above the deposition hood. The air outlet assembly includes an air outlet perforated plate and an air outlet array perforated plate. The air outlet array perforated plate is located below the air outlet perforated plate. The movable plate assembly is slidably connected to the air outlet array perforated plate. A partition is provided below the deposition hood. The movable plate assembly is slidably connected to the partition. An air inlet is provided on the partition.

7. A carbon-carbon composite material production process, adapted to the directional flow CVI flow field structure described in any one of claims 1-6, characterized in that, Includes the following steps: Carbon fiber preforms are prepared using the S1 three-dimensional weaving method, and the density of the carbon fiber preforms is controlled between 0.43-0.45 g / cm³. S2 treats the carbon fiber preform at 300℃ to harden the soft fibers into a hard state. S3 adjusts the flow field structure of the directional flow CVI according to the size of the carbon fiber preform, places the carbon fiber preform into the deposition furnace, and then evacuates to <1KPa to remove air from the furnace and ensure the vacuum level inside the furnace. S4 is heated to 1000-1100℃, and the vacuum degree is maintained at 2.5-3KPa. Then, carbon source gas is introduced and 20% nitrogen is mixed in as a carrier gas to improve density uniformity. When the S5 process is 2 / 3 complete, change the furnace pressure to 2-2.5 kPa to avoid large-area crusting and carbon black formation due to restricted airflow. After the S6 densification process is completed, the vacuum system is shut off, and nitrogen protective gas is introduced to atmospheric pressure. The gas is continuously introduced until the furnace temperature drops to room temperature, at which point the nitrogen introduction is stopped, and carbon / carbon composite material is obtained.

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